In recent years, with the rapid development of electronic technology and image processing technology, image or vision systems are widely used in various industries such as traffic monitoring, driving assistance systems, public security, frontier customs, sports event reporting, event detection, tracking, scene analysis and classification, object detection and recognition, image indexing and retrieval and many other fields. In most image or vision processing applications/systems, such as digital photography, medical image analysis, remote sensing, LCD display processing, and scientific visualization, image contrast adjustment may play a key role.
In general, images/videos have poor contrast due to a number of reasons (e.g., the distribution of the grayscale values of the images is relatively concentrated), for example, the quality of the imaging device used is poor, the operator is inexperienced, unfavorable external conditions (such as rain, snow, smoke, fog, dust, dust, etc.) when the image is being captured and the like. These reasons may result in a lesser dynamic range of the acquired image. Therefore, such an image or video may not display all details in the captured scene, and the captured image may appear faded and unnatural. In addition, the grayscale values of some images may be concentrated in narrower intervals, which may also cause the image details to be not clear enough. For example, an overexposed image with its grayscales concentrated in the high-brightness range, and an underexposed image with its grayscales concentrated in the low-brightness range. In general, contrast enhancement techniques, such as histogram equalization, may be employed to pull apart the gray-scale values of an image or to average the gray-scale values, thereby increasing the dynamic range of the contrast, making the image clearer in detail, and enhancing the contrast.
However, contrast enhancement techniques, such as histogram equalization techniques, may result in issues such as voids in the output histogram, excessively enhanced output, failure to provide control parameters and/or uncontrollable noise and banded interference, and so on.
Therefore, an improved image grayscale value adjustment scheme is demanded.
It should be noted that, information disclosed in the above background portion is provided only for better understanding of the background of the present disclosure, and thus it may contain information that does not form the prior art known by those ordinary skilled in the art.